Generally, a control center (head end) apparatus in the CATV system of this type comprises a VHF antenna, an UHF antenna, and a BS antenna for receiving broadcast waves of existing broadcasting stations, and the broadcasting signals received by these antennas are respectively processed and mixed before being transmitted via a transmission line, which may be for example, a coaxial cable.
The control center apparatus also comprises a video camera, a video tape recorder (VTR) or the like, used as a source for broadcasting independently produced programs, and is constructed so as to select one of these sources.
The control center apparatus determines from which source the signal should be obtained according to the program broadcasting schedule. The center apparatus modulates a TV signal from the selected source to have a specific channel frequency, and mixes the TV signal with other signals before transmitting them via the transmission line.
Further, the control center apparatus transmits data such as channel data and permission or prohibition data for receiving a specific program to a subscriber terminal unit in the form of an FSK signal on a channel prepared in advance.
Each CATV terminal unit has a unique address by which only the terminal unit belonging to a subscriber to chargeable programs is allowed to receive the chargeable programs. Thus, each terminal unit processes the FSK signals transmitted as out-band data from the control center apparatus, and only the terminal unit which has received the permission data is allowed to select a desired signal out of signals transmitted via the transmission line based on the result of the process. Further, only the terminal unit with permission descrambles the selected signal if the selected signal carries a chargeable program and has been scrambled by the control center apparatus, and modulates the descrambled signal to a signal having a specific channel frequency, e.g., channel 1 or channel 2, of a television receiver 4 before outputting the signal.
The CATV terminal unit further comprises an input unit provided on the main body thereof, or an input unit separately supplied as a remote control unit. Operation of this input unit executes channel selection.
The above-mentioned CATV system has an additional function of supporting the watching of programs on a so-called "pay per event" basis, in which "realtime" broadcasting such as a title match or a concert can be watched by applying for the program by telephone.
In the "pay per event" function, the operation at the control center apparatus registers data such as a subscriber's number and program information on a desired program by operating a key or keys of the input unit so that permission data is transmitted to the subscriber when the desired program is broadcast, thereby allowing the subscriber who has applied for the program to watch the program.
As described above, in the conventional CATV system, even though the subscriber applies for a program by telephone and the operator who receives the application at the center apparatus registers the application, the data for permitting the subscriber to watch the program applied for is not transmitted to the subscriber until the applied program is actually broadcast. Accordingly, the subscriber who has made the application by telephone is not notified whether he or she can watch the applied for program until the applied for program is actually broadcast. This causes anxiety in the subscriber.
In view of the above problem, the present invention provides a CATV system and a CATV terminal unit therefor, in which the subscriber may confirm at any time after the application has been made by telephone whether or not he or she has been permitted to watch the applied for program.